1. Technical Field
The present disclosure relates to a secondary cell and a manufacturing method thereof.
2. Description of Related Art
In relation to a secondary cell and a manufacturing method thereof, for example, Japanese Patent Application Publication No. 10-261441 discloses a non-aqueous electrolyte secondary cell with the object of inexpensively producing a highly-reliable joint between a power generating element and an external terminal of the cell while reducing variation in internal resistance (see JP 10-261441 A).
In the manufacturing method of a non-aqueous electrolyte secondary cell disclosed in JP 10-261441 A, the end edges of electrodes are inserted into grooves of a current collector provided with slits at the top, and the leading ends of the end edges of the electrodes are protruded from the slits. Then, the end edges of the electrodes protruding from the slits are laser-scanned to thereby weld together the electrodes and the current collector.
Japanese Patent Application Publication No. 2007-265846 discloses a cylindrical cell and a manufacturing method thereof with the object of reducing internal resistance by adopting a welding structure that allows a current collector to be stably welded to an exposed core portion (see JP 2007-265846 A).
The cylindrical cell disclosed in JP 2007-265846 A has a spiral electrode group with exposed (positive and negative) core portions, and (positive and negative) current collectors welded to the spiral electrode group. The exposed core portion has a fold-down groove that is formed by partially folding down the exposed core portion from the outer circumferential side toward the center of the spiral electrode group. The current collector has a circular flat main body in which a plurality of substantially U-shaped grooves extending radially from the center is formed. During the manufacturing process of this cylindrical cell, the current collector is disposed on the spiral electrode group so that the substantially U-shaped grooves are fitted into the fold-down grooves. Then, the bottom surface and the side walls of the substantially U-shaped grooves are irradiated with a laser beam to thereby weld the current collector to the spiral electrode group.
Japanese Patent Application Publication No. 2007-149353 discloses a prismatic cell used for high-current applications, such as electric vehicles and hybrid electric vehicles (see JP 2007-149353 A).
The prismatic cell disclosed in JP 2007-149353 A has a rolled flat electrode group, and a retainer plate having a folded part into which a plurality of exposed portions of a positive core or a negative core extending from the electrode group are inserted. During the manufacturing process of this prismatic cell, the plurality of exposed portions are irradiated with a laser beam through a slit formed in the retainer plate to thereby integrally weld together the plurality of exposed portions and the retainer plate.